Continuity mistake: When everybody comes to Squidward's house to persuade him to write a letter, you see that all the paper and pencils and bottles on the ground disappear.
Continuity mistake: In the morning when they all wonder where Santa is, and Spongebob keeps singing "Santa's coming tonight", once everybody walks away, Patrick appears right next to Spongebob.
Continuity mistake: When Spongebob is trying to get Squidward to write a letter outside, at the first shot of Spongebob, he's standing straight on the wood step thing, but the next shot he's facing to the side.
Continuity mistake: The picture that Squidward takes of Spongebob is different than what Spongebob is doing when he takes it.
Other mistake: At the Krusty Krab, SpongeBob tells Squidward to write a letter. Patrick then tells SpongeBob that he ripped his paper, and SpongeBob's shoes lose their colour mid-shot. (00:06:45)
Continuity mistake: During the song, "The Very First Christmas," when Squidward is under the mistletoe hanging on SpongeBob's door frame, the door to SpongeBob's house is missing. (00:09:25)
Continuity mistake: After Squidward finishes giving away all his stuff, in the close-up of him as he says, "Am I insane?", not only is the yellow door knob on the left side instead of the right like in the last shot, but it also turns into a gray door handle. A shot later, it's back to a yellow door knob on the right side. (00:20:05)
Continuity mistake: The door to Squidward's house opens inward throughout the episode, but when Squidward comes out of his house on Christmas morning, the door opens outward. (00:13:49)
Continuity mistake: The doorknob on Squidward's house is either on the right or left side of the door throughout the episode, and it is even missing entirely in some shots. (00:11:30)
Other mistake: When SpongeBob has his picture taken, his tie is missing.
Other mistake: When Squidward opens the door to his house on Christmas morning, the door incorrectly overlaps the snow decoration on his house. (00:13:49)
Continuity mistake: In "Jellyfishing" when Squidward gets home from the hospital, Patrick exclaims Merry Christmas! However, later on in the series it is revealed that nobody in Bikini Bottom even knew what Christmas was.
Suggested correction: The episodes are not always meant to be in chronological order. It's entirely possible that "Christmas Who?" took place before "Jellyfishing."
